Distant control system for electric motors.



G. A. PIERCE.

DISTANT CONTROL SYSTEM FOR ELECTRIC MOTORS.

APPLICATION FILED AUG.9, 1911.

1,133,663. 7 Patented Mar. 30, 1915.

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1,133,663. Patented Mar. 30, 1915.

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GEORGE A. PIERCE, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO WILLIAM CHAMP & SONS SHIP & ENGINE BUILDING CGMPANY, OF PHILADELPHIA, PENN- SYLVANIA, A CORPORATION OF PENNSYLVANIA.

DISTANT CONTROL SYSTEM FOR ELECTRIC MGTQRS.

Specification of Letters Patent.

Patented l'iIar. so,

Application filed August 9, 1911, Serial No. 643,160.

To all cr /mm it may concern:

Be it known that I, GnoncnvA. PIERCE, 'a citizen of the United States? residing at Philadelphimin the county of Philadelphiaand State of Pennsylvania, have invented,

certain new and useful lmpr-owemerits in Distant Control Systems for Electric Mofrom any other source of supply. A veryimportant use of the invention is on isolated plants, and for this reason it is particularly adapted for ship propulsion and'especially submarines where it is essential to a good working operation to govern the movements of the vessel from-some particular point irrespective of the location of the apparatus which delivers and converts the current into power and to provide for charging the batteries by the electrical machinery in the vessel when cruising on the surface or at the dock. I

To these ends, my invention comprises a group of motors and adjacent contactor pancl through which they are supplied with current, a switchboard equipment for connecting the batteries in various relations to the motors either for the renewal of thecharge or the'supply of power, and hand operated controlling mechanism located at any desired distance to connect these several pieces of apparatus in proper working relax tion.

It comprises also an equipment of the kind outlined above in combination with overload and reverse current protective devices to insure the opening of the circuits. when dangerous conditions arise.

In, carrying out my invention, I provide a source of electric energy as storage batteries with means for coupling them in charging and discharging relation to an electric unit or units, acting as desired either as a generator or motor, with means for connecting the unit either with a prime mover or propelling apparatus, the charging or power.

connections being made by a group of magnetically operated switches in control circuits leading to a distant station; by these means the navigator is given absolute control of the movements of the vessel and of the condition of the source of supply and the direction or speed of propulsion may be varied at will.

I preferably employ in the main circuit, at a point close to the motors and to the source of supply, a -contactor panel with a suflicient number of automatic switches of breaking capacity to give effective and safe control, a motor switchboard, and :1- battery switchboard, all connected with a master controller by a group of'small wires, thus providingat the navigatofs station absolute command of the movements of the vessel. I preferably provide four el tric units, one pair acting on the starboard, and the other on the port propeller, and two prime movers, one for each pair, by which they may be driven when (onnected toact as generators, and to this end I provide for each pair two couplings or clutches, one to connect with the prime mover and the other with the propeller, I also prefer to provide two separate batteries or sources of voltage supply subject to the automatic switch control already referred to,- by which they may be connected in' series or parallel and in charging or discharging relation to the lectric units and whereby either may be a reserve in case of damage to the other. I preferably employ a compound hand operated master controller consisting of a reversing and speed cont-roller operated by a handle common to the two,-and an auxiliary battery controller. both of these devices or duplicates being at the control station or stations where the movements of the vessel are directed, communication with the controlled apparatus located in the hold of the vessel being by means of a cable of Small control wires above referred to. The speed of the motors is varied by armature and field resistance, and series or parallel connection to the motor units, as \vellas series or parallel relation of the two supply sources, the field magnets of the units being excited by battery current, and ti emotor loads equalized. by an equalizing rheostat on the switchboard, whose compensating resistance may be adjusted to the best working relation. This rheostat serves the dual function of equalizing the load of the propelling units, and acting as a discharge resistance for the field magnets when the motor circui s are opened. The navigator may from a control station place either pair'of units on either source of current supply in case it should be necessary through the disablement of eitherof the storage batteries. In connection with the automatic contactors for varying the resistance of the armature circuits of the propelling units and for coupling them in series or parallel to vary the speed, I provide for additional speed variation through series or parallel battery connection, and a fieldre gsistance governed by the master controller to weaken the strength of the field magnets of the motors, and thus further increase the sped variation by about twenty-five per cent. On the contactor panel for providing the desired armature connections, -I employ nine automatic switches or contactors, a reverse current relay for opening the circuit in case of reverse flow of energy from the.

batteries, and an overload relay to afford necessary safety "When-the motors function either as generators or as motors; and to render these auxiliary devices elfective I provide for resettingthe overload circuit breaker, in case it operates, when the controller is brought to the off position. By operating the master controller, the motors are first brought to hai speed through a number of starting points, then to full speed in parallel through the same starting points, and then to maximum speed by weakening the motor fields. The motor switchboard is provided with a group of double throw switches, these switches when in one position putting the batteries in charging relation to the motors through the contactors which serve as automatic circuit breakers and in the opposite position placing the. contactors in circuit with the master controller, contactor paneland motors in discharging rela-' tion. In my preferred embodiment the reverse current and overload relays are provided with compound windings, one being a potential coil across the battery terminals, and the other a coil in series with the/line. In the overload relay the potential coil serves tohold the relay in position to break the main circuit after it has been lifted by an other when the batteries are being charged and the relay remains in position to keep the charging circuit closed. If the current in the charging circuit should reverse, the potential and series coils would act in conjunction and, lifting the relays, cause the main circuit to open. Auxiliary distribution circuits are provided for connecting the source with lighting, power, and heating circuits hroughout the vessel. 5

My invention embodies various novel features in the system outlined above, whith will lie-definitely indicated in the claims appended to this specification.

In the drawings Figure 1 grammatically the dilferent control and operating circuits, and the'seve'ral types of apparatusI employ for operating one motor unit; Fig. 2 is a simplified diagram of the motor circuits and line switches for varying the power and speedtand Fig. 3 is a'detail view showing the form of master controller I prefer to employ.

Referring now to Fig. 1, the diagram shows one half of the complete operating equip ment for my control system as particularly adapted for use in controlling a submarine vessel. As the other half is identical, except for certain parts common 'to the two, as the batteries and their control apparatus, it is deemed unnecessary to illustrate it. broken bus-bars indicated at 55 and the dotted leads 55 55 55 55 55 55 the latter being connected with a duplicate motor switchboard similarly 0 Y lead to an identical equipment, both e uipments being supplied by the common pair of batteries or multiple voltage source and the common battery switchboard X. The motor switchboards are indicated at Y, the main contactor panels at Z, power and charging units at IV, and a master control apparatus at V, and reversing controller at T.

illustrates dia- The Each contactor operating coil is connected tion of Fig. 2, from which it will be seen that when the series contactors are closed both armatures are connected ,in series through a resistance on each side of the line, and the resistance may be cut down by closing contactors A, B, C, D, E, F, by steps, then opening them and repeating the operation with the parallel contactors P and P closed and 5 opened.

.lt will be seen from the developed master controller shown on the diagram that there are twenty-one steps, eleven of which are used for the series and parallel connections of the motors, and ten to cut in the motor field resistance to increaseits speed.

FE and ER are field and equalizing rheostats for adjusting and balancing the fields of say the port driving units W. The battery switches for connecting the source of supply in series or parallel are magnetically positions, right and left, and the speed con troller progressively cuts in the automatic switches, and cuts out armature resistance with the two units acting in series, then cuts in the resistance and couples the motors inparallel, then cuts out the resistance again and progressively weakens the strength of the field magnets. These several relations will be more readily understood by tracing the several operating conditions of the motor. 'llip wires connecting plusand minus poles of the two batteries with battery switchboard X are duplicated on the companion motor switchboard corresponding to Y, and the leads from the companion motor switchboard and the battery control cylinder U, also are in indentical relation. These leads are indicated in dotted lines at 55*, 55 55, 55, 55 and 55.

The switches l, 2, 3 of the port motor switchboard Y are double throw, and when thrown to the up position place the batteries in charging relation to the port motors, (acting as generators) and close the circuit to the port motor fields, completing the circuit also through the overload and reverse current relays and certain of the contactors on the port contactoh panel, as will be hereinafter described. When these switches are thrown to the down position, the batteries are put in discharging relation tothe motors through the master controller. and as the handle of the latter is turned the proper contactors are operated to throw the battery upon the motor armatures through the regulating resistances. The operation of the battery connecting cylinder ll connects the battery sections to the bus-bars in series or parallel. Switch No. 1 gives selective control on the motor switchboard of the two sources of supply, closing the control circuit on the aft battery in the up position and on the forward battery in'its down position, so as to discharge either battery. This connects the'motor fields and all auXil-' iary circuits to tie battery through switches Nos. 2 and 3 on the motor board. Assuming that thebattery connection cylinder U is thrown to the left for series relation and the switch 1. is closed in its down position, the supply will be connected for maximum speed over the following circuit: from the negative pole of the forward battery to contact O of switch 1, through the left arm of switch 1 to switch pivot and lead 13, thence across the battery cylinder to lead B thence from the automatic coil of switches 56, 57 to B thence across the battery controller to 5*", and from E to the right pivot of switch 1 and across the right arm of switch 1 to positive side of the battery. Automatic switch .38 is also closed in its down position over circuit B B and B, B This operates the switches on the battery switchboard and connects the batteries in series. Assuming the battery controller to be thrown in the opposite direction the batteries would be connected in parallel for half speed over a c rcuitas follows: minus pole of forward battery (3. left arm of switch 1 to left pivot, thence by B and B B B B, B, P, including coil of switch 58, plus pole of battery. closing the switch. The direction and speed handle see .l ig. 3) being moredt'orward operates the controllers V and T (Fig.

1 and gives the vessel ahead motion, the

operating circuits being as follows:-lhc field magnet circuit may be traced from the negative pole of the for a rd battery to point t) of switch 1, then to switch 3, wire X to the iield reversing cylinder T, thence by X, switch. 2, 7 to the field of motors \V, through both fields in series and wire 7" back to point f". Between the field and equalizing rhcri stats a wire 7" 7' extends from a point hetwcin the two fields to the pivot of the swit 1h arm or the equalizer rheostat ER, thus permitting a relative adjustment or balance of the fields to be made. From the point f in the field connections just tracer the -ircuit leads across the middle arm of switch 2, which is now on the down position, to wire to the lowermost contact 31 of the field resistance."thence through the field lcsistance to contact 40 and field reversing cylinder to X,thence to right arm of switch 2 to its pivot, thence to the right pivot of switch 1 and across right switch arm to plus pole of the battery.

For reversing the motion of the motors the connections are as follows:-negative pole of forward battery switch 1, switch 3, X field reversing cylinder, contact 40 oi field resistance, across resistance to contact 31, wire X switch 2, f fields, and

I will now trace the several controller posi tions and the control circuits for establishing them,-and the operating motor circuits from the source of supply through the switches closed by the contactor's.

First controller positlon.-Froin the positive side of the forward battery to point P.

right arm of switch 1 to its pivot, thence to switch 2 and across its right arm to the contact, thence to the controller finger by lead marked feed and across the master cylinder to the series finger, thence to the operating coil of the series contactors to a wire 41. leading; to the switch of the overload relay OB and by wire e2 and wire 44 through a resistance at h to point a over the series contactor wire 46 to line minus 1, switch 3, switch 1, 0, forward battery minus. This is a holding circuit for the series oontactor which by reason of the resistance 15- gives only current enough to hold the contactor closed but not enough to lift it. The lifting circuit is to point 52 as above tracedthence by way of bridging contacts at the top of contactors A, B, C, D, E, F, over wire 5% to point z and return by wire 46, this path not including the resistance h. This circuit actuates the plunger of the series contactor, closing an armature circuit. as. follows through thetwo motors in series. Plus pole of forward battery to the bus-bar through the series coil 82 of reverse current relay RUE, resistance wire r through resistance r, armature, (161 cc across the switch of contactor S, armature lead c through the second motor armature to armaturedeadc thence through section r of the armature rcsistancc,series coil 800i overload relay OR to the bus-bar and-negative pole of aft battery,

thus putting both armatures in series with one section of resistance on each side in circuit, the position indicated in the-simplified diagram of Fig. 2 when the series contactor ulone is closed.

i'b ccom'l controller positiom ln the second position the circuit may be traced from thc positive pole forward battery to P, switch 1, switch 2, feed, master controller cylinder, and the series contactor coil as before, but cutting in also through the controller finger :26, the operating coil of contactor D,

this circuit including in the return path an electrical interlock completed by the series con'tactor at'z to wire 46 and line minus 1,

contactor S, a a armature resistance r overload relay, to negative main connected to the negative side of the aft battery.

' Third controller position.Positive side of forward battery 1?, switch 1, switch 2, feed finger, master controller, series finger and its lead, series contactor coil, wire 41, overload switch, wires ee; 43, 4.4:, 45, 46 to negative pole of battery, as before; another circuit including coil of contactor D,

through finger 26, and master controller, as

before; a third through iinger'lfi and master controller to contactor coil A, and to the return point a through the overhead bridging contact completed by the series contactor to the negative return. vThis operates thev armature switch of contactor A, in addition to the contactors of the second position, and puts? sectionr of armature resistance in parallel with r thus increasing the speed of the motors. v

Z ourthcontrollcr position.-Positive side of forward-battery P, switch 1, switch 2, feed, master controller, series contactor coil,

as before; finger 27, contactor coil E overthe return route by the interlockbefore traced. In this controller position, contac- -tor s A and D are still herd closed. and armature resistance r is put in parallel with resistance r, and r, further increasing the motor speed. i

Fifth controller position-in this position contactor switch B is closed by engage- ,ment with finger 17, and contactors A D E and the series cont-actor being maintained closed over the paths before traced. This puts armature resistance r and r in parallel with r, thereby still further lowering the resistance in series with the armature.

Sloth controller positl0n.-In this position the A B D 1) series contactorsare still maintained, F contactor switch 18' closed by finger 28 andwire 46 to the motor switchboard, thence by wire 28 to the operating coil of contactor F. This. closes F, and as will be seen by the s1m-' plified diagram short circuits all resistances of armature cc and further increases the.

speed of the '1notor.-

Scrcuth controller position-in this controller position contactor C is closed by way of finger 18 wire e7; switch 3 on motor Switchboard, wire 18 thus short-circuiting through contactor C all the resistanceof arniatures a a In this position of the master controller all resistances inthe armature circuits are cut out for the next posi tion which is that of parallel connectionot the motors.

Eighth controller position-In this posi tion thecontroller finger parallel, 1 is engaged and contactors A B D E F C and S. are opened, cont-actor coils P and P becnergized over leads &8 and 49 and contactor operating coils to return by wires a1, e, 46, line minus 1 before traced. Switches P and P being closed, and A, B, C, D, E, F, being opened, the motors are now in parallel with all resistance cut in.

The ninth to the twelfth master controller position successively engages the fingers which control contactors A, B, C and D, E, l? for the two motors in pairs, paralleling the resistances of A andl) and B and E, and thenshort-circuiting them by the final closure of C and which places the motors in pa *allel with no resistance in the armature circuits. liurther movement of the master controller then progressively disengages fingers 31 to l0, across which the field resistance is connected, gradually cutting more and. more resistance into the held circuit and further increasing the speed of the motors through a range of twenty-five per cent, during which the fingers controlling the parallel contactors remain unchanged on the master controller. The several contactors are provided with an auxiliary resistance 50, normally bridged or snort-circuited, and when the coil is operated this short-circuit is opened.and the resistance out in. This saves energy and prevents heating of the operating coils.

' Each of the coils also carries an insulated bridge piece which breaks the return circuit in its attracted position, thus providing an electrical interlock between several contactors. The action of the bridge piece or the series contactor on this over-head wiring connects wires 5% and on the'return circuit. A similar arrangement is provided for the bridge piece of contactor 1 while P plus P complete an interlocking return circuit through wire 48 for the contactors A, B, C, D, E F. Similarly, the contactors A, B, C, D, E F, normally complete bx bridging contacts a' return circuit through bridging contact of the series contactor controlling the return current through the point and wire 46. and the reverse cu'rrent relay carries a bridging contact 51 in a negative return circuit by way of parallel contactors and lead marked Par. 2 terminating in the contact engaged by switch 2 in its upper charging position, so that the actuation hyreversal of battery on bridge.

ergy will open the return circuit at 51 and insure the opening of the main circuit lng against damage to the motors through any failure of the resistance contactors tofunction properly. As will be seen, contactors A, B, C, D E F each have an insulated bridging contact carried by its movable member at the top which normally completes the return circuit for the operating coils and through the bridging contacts of the parallel contactors. through the switch 1 the overload relay, an arrangementwhich insures safety to the system under normal operation. This circuit divides at a point 52, one branch returning by way of the bridging contacts of the series and parallel contactors by way of wires i3, i4; holding resistance, to the negative line 1, and the other branch flowing through the circuit 5i, and bridging contact j; this latter circuit is of course opened when any of the resistance controlling contactors A, B, C, D, E, F are actuated.

With the controller'in #1 position, series contactor closes over bridge on A, B, C, D, E, F, over bridge 3' on series contactor to return'wire 46 as the circuit over 42, 43, 44: resistance It will not permit sufficient current to lift contactor S. Contactor S in operating opens bridge j and resistance h is inserted which'permits suilicient current to hold contactor S in position. Bridges on A, B, C, D, E, F can then be opened and are opened by the contactorsparalleling the armature resistance.

In controller position 8 P and P contactors should operate. This however can not be done unless contactors A, B, G, D, E, F have released and closed the overhead It is also necessary that contactor releasesand closes bridge j to return wire e6 as resistance h in the parallel circuit 42, 43, 4% 2-46 will not permit suiiicient currentto operate contactors P and P This means of electrical interlock insures maxi mum resistance in the circuit and insures contactor S being open when P and P should close. When P contactor closes it gives a return circuit for P P auxiliary operated opening the overhead bridges Without irterfering with P P contactor auxiliary currents. when P contactor closes the overhead bridge closes the circuit for auxiliary wiring for contactors A, B, C, D, E, F t r t rn c rcuit 46;

This current passes current to L6 and A, B, C, D, E, F can be nects through cylinder one being used to reverse the ture resistance and group the motors in series or parallel as hereinbefore fully de scribed. These two cylinders are operated by a single handle which throws 150 degrees on either side of the center for an ahead or -reverse motion, respectively. The arrangement of the controller will be understood from' Fig. 25, in which represents the re vcrsing cylinder, and 61 the motor operating cylinder. A single operating handle cona crank shaft on the reversing with a rod 62 pivoted to a gear sector 63 engaging a pinion 6% on the operating cylinder 61.

The finger board construction is of the usual form, and it has not been deemed necessary to show its structure in detail; the arrangement will be clearly understood from the diagram, Fig. 3.

When the switches 1, 2 and 3 on the motor switchboard are in the up. or charging position the return negative line 1 is open and 'the negative line 2 from the aft battery is in position to supply the operating coils of contactors C and F and P and P and 18 and 8, functioning independently of the master controller, the field magnets being excited through the field and equalizer rheostats; and the armature shaft or shafts are-clutched to the prime mover or movers. A hand operated clutch 65 is placed between the propeller shaft and the 'motor shaft and a similar clutch 66 is placed between the motor shaft (when operating as ,a generator) and the prime mover Gr. Thus it will be seen that the master controller gives complete mastery over the movements of the vessel and may be placed at any point selected, as the bridge, pilot house or conning tower.

It will be observed from the foregoing that when the motors are driven as generators and connected to the battery to charge the same, the main series coils and 82 of the overload relay OR and reverse current re lay RCR respectively carry the charging current, while the potential coils 81 and 83 of these relays are connected acrossthe battery terminals and these relays operate upon overload or reversal of current as 'hereinbefore described, the operation of either of these relays serving to break the circuits of contactors which then release and break he charging circuit. The circuits of the potential coils 81 and 8,3 are completed, under charging conditions, on the boardYso that upon opening the charging circuit at this board the circuits of the potential coils will be broken and the through switches relays, both overload and reverse current, will be re-set. \Vith the connections made for discharge,- that is for the motors to be operated by current from the batteries, the

-contactor circuits will be made independently of the switch 51 of the reverse current relay so that the relay may open without interrupting the contactor circuit. The overload relay will, however-, with connections for discharge, control contactor circuits which will be broken upon excess current in the series coil 80 and will be held in this condition by the potential coil 81 until the circuit of this potential co'tl is broken and the relays re-set as before' ireferred to.

Thepotential coil, with connections for dis-.

charge, has its circuit made through the reverse controller T, which is interlocked with the master controller Y so that the cir cuit of the coil 81 is broken and the overload relays re-set when the master controller ,is brought to the oif position. It will be seen that the contactors which operate as circuit breakers to break the charging cir-. cuit under control of the overload and re-" verse current relays as described, are also employed to control the circuit through which current is supplied from the-batteries to the motors so that no extra contactors, over what are required for the regulation and control of the motors deriving current from the batteries, are necessary to provide circuit breakers in the charging circuit when the motors operate as generators to, charge the batteries.

- Having thus described my invention, I declare that what I claim is new and desire to secure by Letters Patent is:

' 1. In a power generating system, the combination of a plurality of motors, a storage battery, magnetically operated contactors, comprising lifting coils, adapted to connect the motors in series and parallel relations, a circuit for supplying current to the fields of said motors, a distant master controller adapted to control the contactors and means controlled by said controller for supplying current from said battery to the said lifting coils and means controlled by said controller for supplying battery current to the fields of said motors in both forward and reverse operation of the motors, an equalizing resistance and adjusting switching means separate from said contactors and controller for balancing the motor loads.

2. In a power generating system, a plurality of motors, magnetically operated contactors for connecting the motors in series and parallel relations, a source of current supply. all at a common point or station, motor field resistance. a distant master controllerfor the contractors adapted to vary the motor field resistance and operate the contactors for series or parallel relation of the motors, and field discharging and load equalizing resistance in the several motor field circuits, which field circuits are governed'by the master controller.

3. An operating system for electric motors, comprising a plurality of electric inotors, a supply circuit, a group of contactors, for connecting the motors in series or paral lel elation to the supply circuit, control circuits for said contactors, an overload relay comprising a potential winding connected across the supply circuit, a winding in series in the supply circuit, and a switch in the control circuit for the parallel contactors, a master controller governing the contactors, said controller comprising a contact for re setting the overload relay when the controller goes to off position.

l. An operating system for electric motors comprising a plurality of electric motors, a source of supply and a main circuit for supplying said motors extending from said source, a group of contactors for connecting the motors to said main circuit and in series or parallel relation, control circuits extending from said source for operating said contactors, a master controller governing said control circuits and an overload. relay for opening the main and control circuits, said controller comprising means for resetting the relay at the master controller when it goes to oli position.

An operating system for electric motors comprising plurality of electric motors, a storage battery and a main circuit for carrying current between said motors and said battery, a group of magnetically operated contactors for connecting the motors to the main circuit and in series or parallel relation to each other, a distant controller for the contactors, control circuits extending from said controllers to the contactors, an o erload relay for opening both the main and control circuits and a reverse current relay having coils opposing each otherwhen current flows from the motors (as generators) to the battery, one of the said coils being connected in series in the main circuit. and the other across the main circuit, said" reverse current relay being adapted to open both the main and control circuits on current reversal.

6. An operating system for electric motors comprising a plurality of motors. a storage battery in a plurality of sections, supply mains for the motors extending from the battery, a master controller at a distant control station, magnetic switches controlled by said controller and adapted to connect the motors in series or parallel relation, control circuits for the said magnetic switches supplied with current from said battery and controlled by said controller, a )attery controller at the control station, and electrically operated switches governed by the battery controller for throwing the battery sections in series or parallel, and connecting them to the supply mains for the motors.

7. A propulsion system for ships comprising multiple propellers and a plurality of operating motors for each propeller shaft, a plurality of storage batteries, a group of electrically operated cont actors correspond.- ing to each shaft and controlling the motors driving the same, each of said groups of contactors adapted to connect the motors of its set in series or parallel anda single distant master controller common to the contactors of all the motor sets, and circuit connections controlled by the contactors for conveying current from any or all'of said storage batteries to the motors of all the sets. 7 a

8 In a power generating system, a pinrality ot motors, a main circuit for supply ing the motors with current, magnetically operated contractors adapted to connect the motors in series or parallel, a distant controller for the contactors, an overload relay having a winding in the main circuit and governing said circuit through the contactors, and a reverse current relay governing the circuit of the parallel inotor contactors.

9. In a power generating system, a plu rality of motors, a main circuit for supplying the motors with current, magnetically operated contactors adapted to connect the motors in series or parallel, a contactor operating circuit and a master controller for the contactor operating circuit comprising a speed control cylinder and reversing cyl'rn der located at a distant point and operated by a single handle.

10.111 a power generating system, the

combination o1 a plurality of motors, sectionai storage battery as a source or" current supply, contactors for conveying operating current to the motors, bus-bars receiving energy from said battery, a group of magnetically operated contactors adapted to connect the motors in series or parallel, electrically operated switches for coupling the battery sections inseries or parallel and with the bus-bars, all located adjacent to each other at a common station, a manually operated controller at a distant station controlling current supplied by the same source through control wires to operate the contactors and couple the motors locally in series or parallel relation and with a storage battery. said control wires being small with relation to the motor supply conductors.

11. In an electric power system, the combination with a motor, of a storage battery, circuits for conveying current between the battery and the motor, electromagnetically operated contactors controlling the said circuits, there being a cont-actorcorresponding cuits and means for alternately completing the control circuit of said contactors through szucl master controller and completingthe control circuit of certain of seicl contactors lndependently of said controller. 10

In testimony whereof I afiix my signature,

in presence of two witnesses.

GEORGE A. PIERCE. VVitnessesz ALBERT H. THOMAS, GEORGE LFG'ARDNER.

Copies of this patent may he obtained for five cents each. by addressing the commissioner.of Patents Washington, D. C." 

